Apparatus for defrosting refrigerating coils



April 23, 1935. l. G. FURNAS 1,998,575

APPARATUS FOR DEFROSTING REFRIGERATING COILS Original Filed Ma'ich 21, 1952 4z 47 mi IriEf; 1 Ii? 46 43 INVENTOR fsam 6.2217245,

ATTORNEY Patented Apr. 23, 1935 PATENT OFFICE APPARATUS FOR DEFROS'iING REFRIG- ERATIN G COILS Isaiah G. Furnas, Chicago, Ill.

Application March 21,

1932, Serial No. 800,166

Renewed July 12, 1934 11 Claims.

This invention relates to a coil defrosting mechanism and will be described as employed for the defrosting of cooling coils associated with a refrigerator system.

An object of this invention is the provision of mechanism whereby accumulated frost may be readily and quickly removed from refrigerating coils without interfering with the normal operation of the refrigerating system and without the necessity of shutting down the system or any part thereof even for a short time.

Another object is the provision of such a device adapted to break loose the congealed or coagulated oil film from the inner walls of sucha refrigerating coil, more economically and efiiciently than has been done heretofore.

The accumulation of an appreciable amount of frost on the outer surface of a refrigerating coil, or the accumulation of a coagulated film of oil on the inside very materially insulates the coil from the air inthe compartment to be refrigerated. As a result, it restricts the flow of heat from the cooling compartment to the interior of the coil thereby cutting down the efiiciency of the system, and making the system uneconomical particularly when extremely low temperatures are required as in the quick freezing systems because of the additional refrigerating capacity required to maintain the desired low temperature- Heretofore it has been the practice to bypass the refrigerating condenser, and allow the compressed hot gases to pass through the cooling coils, to heat the coils and defrost them. An obvious disadvantage of such practice is that all the cooling coils are heated at one time, thus throwing the entire'system out of operation for a suflicient time to carry out'the defrosting operation. .Not only this, but the heat from all the cooling coils of the system is sufficient to materially raise the temperature of the compartment to be refrigerated, resulting in the rising of the temperature of the stored goods or necessitating their removal before the defrosting operation is attempted. Such a defrosting operation pre vents the maintenance of uniform temperature in thestorage compartment which is very detrimental to the quality of goods which are preserved by refrigeration.

One of the important objects of my invention is, therefore, the provision of a device which will obviate the disadvantages above pointed out, and which will quickly and efficiently defrost the coils by sections while the refrigerating plant is operating and without interfering with the maintenance of a uniform temperature in the storage or refrigerating compartment.

Other objects and advantages of this invention will appear fromthe following description with reference to the accompanying drawing.

On the drawing:

Figure 1 is a perspective view illustrating my invention and showing the refrigerating coils diagrammatically, also illustrating a wiring diagram for electrical connection to the bus bars.

Figure 2 is a perspective view of a switch member adapted to connect the bus bars electrically to the refrigerating coils.

Figure 3 is a perspective view of a form of clamp which may be used for connecting one of the bus bars to the refrigerating coils and for similar purposes.

Figure 4 is a diagrammatic view of one form of my invention.

Figure 5 is a diagrammatic view of a modification of my invention.

Figure 6 isa diagrammatic view of another modification of my invention.

Figure '1 is a diagrammatic view of still a further modification of my invention, and

Figure 8 is a diagrammatic view of a controlling apparatus which may be employed with my invention.

As shown on the drawing:

In Figures 1' and 4 to 7 inclusive, numeral 5 designates a cooling coil for a'refrigerating system. Such a coil usually consists of a large number of connected pipes 6 or a continuous pipe which is bent at the end and folded back) along itself many times or coiled in various manners to best fit the compartment in which it is to be used. If desired, the coils may be in several sections each section being fed by a pipe 8 and discharging into a pipe 9. In Figures 4, 5, and '7', only sections of the coil are shown with the other sections broken away for the purpose of better illustrating my invention as in operation.

In Figure 1, the horizontal bus bar II is connected to a vertical bus-bar l2 which in turn is electrically connected by suitable clamping members I4 to portions of the coil 5 and if desired, to the ground as indicated at IS. The bus bar I6 is similarly connected to a vertical bus bar I! disposed adjacent the coil 5 and having thereon horizontally projecting contact portions l8 adapted to be connected by switch blades l9 see Fig. 2 of any suitable design to the horizontally contact projections 2| on the clamping members 22 which are connected at intermediate points on the coils 5. By this arrangement, it is possible to place the switch blades it in such a position that they bridge the contact portions 18 and 2! either near the upper end or the lower end of the vertical bar I? thereby selectively connecting the bus ll with intermediate points on the coils 5.

The form of switch shown in Figure 2 comprises blades i9 extending parallel and supported by side bars 25. Plate members 25 are interposed between the bars 25 and the blades 19 for holding the ends of the bars 25 spaced from the sides of the blades i9 to accommodate t1 down wardly extending prongs 2? of the fork member 28 to which the handles 25 are secured. The fork members 28 are preferably of spring material to exert a pressure on the ends of the blades i9 and permit yielding of the blades laterally as they are pressed upon the cooperating contact portions l8 and 25.

The clamp M shown in Figure 3 is preferably formed of copper strapping or the like. It is preferably provided with openings 3! and 32 through which bolts may pass and by which the clamp may be securely held upon the refrigerating pipe and upon the bus bars.

In the operation of the system of the type disclosed, it is necessary to force a relatively large electric current through the coils to heat them, the current being of relatively low voltage so as not to be dangerous. It is important, however, in applying the switch [9 and in removing the same, that the secondary 35 of the transformer 36 should be dead in order that the operator may not be burned by an electric arc. To determine whether or not the secondary is dead, I have provided a signaling system consisting of a buzzer 3! and a bell 3B permanently fixed directly across the secondary line so that whenever the secondary is excited, the signal will sound and be a warning to the operator not to touch the switch iii. In the secondary circuit I have also included a choke coil 39 to restrain surges which'might otherwise be set up. The primary 4| of the transformer 36 is adapted to be connected directly above the line 42 by means of a switch 43, which is actuated by a coil 44 when the push button 45 is pressed down upon the contact points 46 and 47 to bridge the same and close the circuit therethrough. As the switch 43 is closed, a switch blade 49 is also closed upon the contact 5| which completes a holding circuit for the switch 43. In order to open the switch 43, it is necessary to press the push button 52 to break the connection between the contacts 53 and 54, thus interrupting the holding circuits for the switch 43.

In Figure 4 I have shown a common bus bar l2 connected at two points on the coil 5 and the secondary 35 of the transformer 36 connected between the bus bar l2 and an intermediate point 2| on the coil 5. In the modification shown in Figure 5, the coil 5 has interposed therein at certain points insulating couplings 56 which divide the coil 5 into a plurality of sections electrically insulated from all other sections. By this arrangement it is possible to connect the opposite sides of the secondary 35 of transformer to the coils 5 adjacent the insulator 56, without danger of causing stray currents to pass through other portions of the coil.

In Figure 6 the bus bar l2 connects several points E4 on the coil 5 but it is not directly connected to the transformer. In this case, the transformer is connected to intermediate points 58 and 59. If the bus bar 12 is grounded as at [5, in Figure 6, the opposite ends of the transformer secondary 35 impress potentials on the coil 5 at the points 58 and 59 which are higher and lower than ground potential but no stray currents pass through other coils that may be me tallic connected therewith because the potentials impressed at 58 and 59 are reduced or increased as the case may be to ground potential at the points i 4.

In Figure 7, I have shown a transformer having a primary 52 with a secondary divided into two sections 63 and 64 so connected with the coil 5 that the same potential is impressed on the coil 5 at the points 65 and 66 and a return conductor is connected between a central point on the transformer as at El, and to an intermediate point 68 on the coil 5.

The diagrammatic illustration in Figure 8 represents an automatically operable control arrangement for closing the switches in the primary and secondary circuits of the transformer. The supply line is designated by numeral 42 and is connected to the conductors H and T2 which lead to the primary of the transformer 4| but is interrupted by the spaces between the switch contacts I3 and 14, which are adapted to be closed by the relay coil 15 upon closure of the contacts TB and T7. The switch contacts 8! and 82 when closed complete the circuit through the secondary 35 of the transformer. These contacts BI and B2 are adapted to be closed by the coil 83 when its circuit is completed through the contacts 84 and 85. The contacts 84 and 85 are closed by the coil 83 upon closure of the contacts 84 and 85. At 8! is designated a pushbutton and holding circuits therefor in the conductor 88 adapted when actuated to close the circuit through the control motor 89 which actuates a suitable form of contact drum or other control mechanism arranged to close the con tacts B4 and 85' when actuated excite coil 83 and close contacts 84 and 85' to excite the coil 83 and close the secondary circuit of the transformer and hold the same closed while the contacts 76 and 11 are closed to excite the coil 15 and effect the closing of the contacts 13 and I4 to close the primary circuit of the transformer..

After the primary circuit has been closed a pre determined length of time it is again automatically opened before the opening of the secondary circuit.

By this arrangement it is possible to automatically close consecutive electric circuits through various sections of coil 5 and defrost the refrigerating coil section by section without interfering with the operation of the refrigerating plant and without interfering with the maintenance of a predetermined and constant temperature in the cooling compartment. It is possible to use many different forms of controlling apparatus to accomplish the connection of and disconnection of the circuits and I have illus trated diagrammatically in Figure 8 one such controlling apparatus by which the device may be operated.

I am aware that this device is susceptible of various changes and modifications without departing from the principles of this invention and I do not intend to limit the patent granted hereon except as required by the prior art.

Iclaim as my invention:

1. In a device of the class described, in combination, a refrigerating coil, a bus bar connected to said coil at a plurality of points, a second bus bar disposed adjacent said coil and adapted to be selectively connected to said coil at a plurality of points intermediate the first mentioned points, automatic means for connecting said bus bar selectively to different points on said coil and subsequently connecting and disconnecting a source of potential between said bars.

2. In a device of the class described, in combination, a refrigerating coil, a bus bar connected to said coil at a plurality of points, a second bus bar disposed adjacent said coil and adapted to be selectively connected to said coil at a plurality of points intermediate the first mentioned points, automatic means for connecting said second bus bar selectively to different points on said coil and subsequently selectively connecting and disconnecting a source of potential with certain of said points of connection to complete an electric circuit through portions of said coil.

3. In a refrigeration system, a metallic refrigerant carrying pipe formed of a plurality of sections, said sections being adapted to form a part of an electric circuit, and insulating means connecting the sections adapted to ofier a high resistance to current flow between the sections.

4, In a refrigerating system, a metallic refrigerant carrying coil, a bus structure positioned adjacent said coil, switch contacts on said bus structure, a source of current connected to said coiland to said bus structure, switch contacts carried supported by said coil and in conductive contact therewith, and switch means adapted to connect said bus switch with said coil supported switch contacts whereby sections of said coil may be selectively placed in circuit with said source.

5. In a refrigerating system, a metallic refrigerant carrying pipe, a source of current having terminals of opposite polarity, means to conductively connect a portion of said pipe to said terminals and in circuit with said source, and conductor means connecting portions of said pipe extending on either side of said first named portion to the electrical neutral of said circuit and to ground.

6. A refrigerating system for cold storage rooms and the like, said system comprising a metallic refrigerant carrying coil, and means to defrost portions of said coil while the system is normally active, said means comprising a plurality of relatively spaced switch contacts mounted supported on said coil to define between said contacts circuits of relatively short length, a bus structure having a plurality of switch contacts positioned selected portions of said coil in circuit connection with said source, and conductor means connecting a plurality of points on said coil and to ground to maintain said connected points at ground potential.

7. In a refrigerating system, means including a metallic refrigerant carrying coil forming a closed conducting loop, a sourceof energy having terminals of opposite polarity, meansto connect a section of said coil to said terminals to form an electric circuit, and conductor means connecting a point in said section intermediate its connection to said terminals in conductive connection with points on said coil extending on either side of said section, and other conductor means connecting said first named conductor means to ground.

8. In a refrigerating system, a metallic refrigerant carrying coil having a plurality of connected sections; conductor means connecting the ends of said sections to maintain said ends at a common electrical potential, a source of .current having one of its terminals connected to said conductor means, and means adapted for connecting the other terminal of said course to selected points in said sections to include portions of said sections in circuit connection with said source.

I 9. The method of defrosting a refrigerating coil composed of a plurality of fluid connected sections which consists in conductively connecting the ends of the sections tomaintain the ends at a common electrical potential, and connecting selected portions of the sections in circuit with a source of current having one of its terminals connected to the means conductively connecting the ends of the sections. 1 I

10. The method of defrosting a portion of a refrigerant carrying metallic pipe while the refrigerating system is normally active, which method consists in including a portion of the pipe in circuit with a source of current and in connecting portions of the pipe extending on either side of the first named portion to the'electrical neutral of the circuit and to ground.

11. The method of defrosting a portion of a refrigerant carrying metallic coil while the refrigerating system is normally active, which method consists in placing a portion of the coil in circuit with a source of current and in conductively connecting portions of the coiloutside of the portion included in the circuit to maintain said portions at a commonelectrical potential, and thereby prevent stray currents in these portions.

ISAIAH G. FURNAS. 

